The pathogenesis of myofascial face pain (MFP), the most prevalent type of temporomandibular disorder (TMD), remains controversial. One of the key controversies concerns the role of sleep bruxism (SB). While relatively weak measures of SB have supported a role of SB in at least some MFP patients, no laboratory based sleep study has been undertaken to resolve this issue definitively. This application proposes as its main aim the conduct of the definitive study of SB in MFP maintenance, in which the separate role of grinding and clenching would be examined. We would also explore the relationship between SB and stress induced bruxism, as well as the role of genetic anomalies in modulating the risk of pain among those with SB. A second aim would evaluate the role of central sensitization (CS) in the maintenance of MFP. Evidence supporting a role for CS in MFP has been limited by biases in the sampling of both patients and anatomic sites. Therefore, we would examine the role of CS in MFP in a more representative sample of MFP patients and controls, as well as conduct an evaluation of CS in both extratrigeminal and trigeminal regions. Differences in CS in these two areas might suggest different pain maintenance mechanisms. Data collected in the service of these two aims then allows the achievement a third aim, understanding the relationships between SB and CS in MFP, including the possibility that elevations in SB and CS may define subgroups in which different pain maintenance mechanisms are operative. These aims can be achieved in the context of a case-control study of 120 MFP patients and 60 demographically-matched controls. Pursuit of these aims will provide firm evidence regarding the role of SB in MFP and will advance understanding of the relationship between SB and CS. This understanding is expected to support our long-term goal of improving clinical treatment of MFP by targeting treatment to underlying pain-maintenance mechanisms.